1. Field of the Invention
The present invention relates to a liquid crystal projector for displaying a picture on a screen by projecting light rays emitted by a light source onto three liquid crystal panels and transmitted by the three liquid crystal panels, and a projection lens unit, an optical unit and a cooling system to be employed in the liquid crystal projector.
2. Description of the Related Art
A prior art liquid crystal projector provided with three liquid crystal panels is disclosed in, for example, JP-A No. 6-289392. This prior art liquid crystal projector comprises, as principal components, a light source, a cold mirror, a blue light reflecting dichroic mirror (hereinafter referred to as xe2x80x9cB light reflecting dichroic mirrorxe2x80x9d), a green light reflecting dichroic mirror (hereinafter referred to as xe2x80x9cG light reflecting dichroic mirrorxe2x80x9d), image reflecting mirrors, a red-light liquid crystal panel (hereinafter referred to as xe2x80x9cR liquid crystal panelxe2x80x9d), a green-light liquid crystal panel (hereinafter referred to as xe2x80x9cG liquid crystal panelxe2x80x9d), a blue-light liquid crystal panel (hereinafter referred to as xe2x80x9cB liquid crystal panelxe2x80x9d), a combining dichroic prism and a projection lens. Light rays emitted by the light source are divided into R, G and B light rays by the light transmitting and reflecting agencies of the cold mirror, the B light reflecting dichroic mirror and the G light reflecting dichroic mirror, the light rays are reflected by the image reflecting mirrors toward the R, G and B liquid crystal panels. The light rays traveled through the R, G and B liquid crystal panels are combined by the dichroic prism and a color picture is projected through the projection lens in an enlarged color picture on a screen.
Such a known, commercialized liquid crystal projector employs three 1.3 in. liquid crystal panels. is formed in a compact construction and is capable of displaying pictures in a high definition.
The foregoing liquid crystal projector is provided with a cooling system for suppressing the temperature rise of the liquid crystal panels.
Referring to FIG. 1 showing a known liquid crystal projector in a side view, a cooling fan 81 (an axial fan in this liquid crystal projector) is disposed below three 1.3 in. liquid crystal panels (only liquid crystal panels 14 and 18 are shown) to blow air toward the liquid crystal panels including the liquid crystal panels 14 and 18 to suppress the temperature rise of the liquid crystal panels including the liquid crystal panels 14 and 18. Since the liquid crystal panels including the liquid crystal panels 14 and 18 are exposed directly to air delivered by the cooling fan 81, the liquid crystal panels including the liquid crystal panels 14 and 18 can effectively cooled. In FIG. 1, indicated at 27 is a projection lens.
The outside size in a horizontal plane of this liquid crystal projector provided with the three 1.3 in. liquid crystal panels excluding a projecting part of the projection lens projecting from a case is 245 mm by 329 mm, and the overall outside size in a horizontal plane of the liquid crystal projector including the projecting part of the projection lens is 245 mm by 380 mm. Such a large overall outside size of the liquid crystal projector is a problem in storing and carrying the liquid crystal projector, and the reduction of the overall outside size of the liquid crystal projector has been desired.
The inventors of the present invention examined a concept about miniaturization necessary to realize a liquid crystal projector more compact than the prior art liquid crystal projector and found that a liquid crystal projector provided with three liquid crystal panels must be formed in the smallest possible outside size suitable for storing the liquid crystal projector in a prevalently used storage cabinet and for carrying the same in a prevalently used carrying case.
The known liquid crystal projector shown in FIG. 1 has a height L2 equal to the sum of the height of a part including the projection lens 27 and the liquid crystal panels 14 and 18, and the height of the cooling fan 81. The liquid crystal projector has a dead space under the projection lens 27, which increases the overall height of the liquid crystal projector.
Accordingly, it is a first object of the present invention to provide a liquid crystal projector of an outside size capable of being stored in a prevalently used storage cabinet and of being carried in a prevalently used carrying case.
Another object of the present invention is to provide a liquid crystal projector having a small height and formed in a compact construction.
A third object of the present invention is to provide a projection unit and an optical unit effective in forming a liquid crystal projector in a compact construction.
A fourth object of the present invention is to provide a cooling system capable of efficiently cooling a liquid crystal projector.
With the foregoing objects in view, the present invention provides a liquid crystal projector having a size in a horizontal plane substantially equal to an A4 folder size, i.e., the size of folders for holding papers of the trimmed sheet size A4. The A4 folder size is 263 mm by 318 mm. The liquid crystal projector of the present invention subjects light rays emitted by a light source to color separation to divide the light rays, projects the divided light rays on a first liquid crystal panel, a second liquid crystal panel and a third liquid crystal panel, combines the light rays traveled through the first, the second and the third liquid crystal panel, and projects the combined light rays on a screen through a projection lens. The outside size in a horizontal plane of the liquid crystal projector is the outside size of a case serving as a housing for the liquid crystal projector. The outside size in a horizontal plane of the liquid crystal projector may be the sum of the size of the case and that of a part projecting from the case. The size of the first, the second and the third liquid crystal panel is 0.9 in. or below. The distance between the display surface of the liquid crystal panel disposed substantially perpendicularly to the optical axis of the projection lens and the extremity of the projection lens is about 146 mm or below. The liquid crystal projector is provided with a color combining optical system including a cross dichroic prism for color combination. The cross dichroic prism has a size in a horizontal plane of 32 mm by 32 mm or below.
A liquid crystal projector according to the present invention comprises a color separation optical system comprising a cross dichroic prism, and a first dichroic mirror, a second dichroic mirror, a first mirror, a second mirror and a third mirror arranged around the cross dichroic prism, an illuminating system comprising a light source, a polarizing device and an optical integrating means, liquid crystal and a projection lens unit comprising a light source power supply for supplying power to the light source, and a projection lens unit comprising a plurality of liquid crystal panels, a cross dichroic prism and a projection lens, in which the projection lens unit, the color separating optical system, the illuminating optical system, and the light source power supply are arranged in that order.
A liquid crystal projector according to the present invention comprises a color separating optical system comprising a first dichroic mirror, a second dichroic mirror, and a first mirror, a second mirror and a third mirror arranged around a cross dichroic mirror, an illuminating optical system comprising a light source, a polarizing device, and an optical integrating means, a light source power supply for supplying power to the light source, and a projection lens unit comprising a plurality of liquid crystal panels, a cross dichroic prism and a projection lens, in which the combination of the projection lens unit and the color separating optical system, the illuminating optical system and the light source power supply are arranged in that order. An exhaust fan is disposed near the light source. A cooling fan and a duct for guiding cooling air delivered by the cooling fan to the first, the second and the third liquid crystal panel are disposed beside the projection lens.
A projection lens unit according to the present invention comprises a projection lens, a cross dichroic prism disposed on the light receiving side of the projection lens, first, second and third liquid crystal panels, and a structural means for arranging the first, the second and the third liquid crystal panel around the cross dichroic prism with the second liquid crystal panel set substantially perpendicularly to the optical axis of the projection lens, in which the distance between the display surface of the second liquid crystal panel and the extremity of the projection lens is about 146 mm or below, and the size in a horizontal plane of the cross dichroic prism is 32 mm by 32 mm.
An optical unit according to the present invention comprises an illuminating optical system including a light source, a color separation optical system for separating light rays received from the illuminating optical system into light rays of three colors, first, second and third liquid crystal panels which receive the light rays of three colors, respectively, and a cross dichroic prism for combining light rays traveled through the first, the second and the third liquid crystal panel, in which the size of the display screen of the first, the second and the third liquid crystal panel is 0.9 in. or below and the size in a horizontal plane of the cross dichroic prism is 32 mm or below by 32 mm or below.
A liquid crystal projector according to the present invention comprises a housing, a first cooling system having a sealed duct including liquid crystal panels, a second cooling system disposed inside the housing to cool the duct from outside, in which the liquid crystal panels are cooled directly by the first cooling system and are cooled indirectly by the second cooling system. The first cooling system is provided with a cooling fan. The size in a horizontal plane of the liquid crystal projector is nearly equal to or below the A4 folder size.
A liquid crystal projector according to the present invention comprises a plurality of cooling fans for cooling liquid crystal panels, in which at least one of the cooling fans is disposed beside the projection lens. One of the plurality of cooling fans is used specially for cooling the liquid crystal panels. The cooling fan specially for cooling the liquid crystal panels has a cooling duct divided into a plurality of sections so that cooling air flows toward the G liquid crystal panel at a velocity or a flow rate greater than that at which cooling air flows toward the rest of the liquid crystal panels. One of those cooling fans is a centrifugal fan.
A cooling system according to the present invention comprises a plurality of liquid crystal panels, a cooling fan, a duct for distributing a cooling fluid delivered by the cooling fan to the plurality of liquid crystal panels, and a plurality of guide members disposed in the duct to adjust the velocity or the flow rate of the cooling fluid flowing to each of the liquid crystal panels. The guide members adjust the flow of the cooling fluid so that the cooling fluid flows toward one of the liquid crystal panels at a velocity or a flow rate greater than that at which the cooling fluid flows toward the other liquid crystal panel. The duct is extended between the cooling fan and the plurality of liquid crystal panels. The duct is formed so as to blow the cooling fluid upward from below the plurality of liquid crystal panels. The duct may be extended from the cooling fan to the plurality of liquid crystal panels and from the plurality of liquid crystal panels to the cooling fan.
A projection lens unit according to the present invention comprises a projection lens, a cross dichroic prism disposed on the light receiving side of the projection lens, first, second and third liquid crystal panels disposed around the cross dichroic prism, a cooling fan disposed beside the projection lens, a duct for carrying a cooling fluid delivered by the cooling fan to the first, the second and the third liquid crystal panel, and a plurality of guide members disposed in the duct to adjust velocities or flow rates at which the cooling fluid flows toward the first, the second and the third liquid crystal panel, respectively.
An optical unit according to the present invention comprises an illuminating optical system including a light source, a color separating optical system for separating light rays received from the illuminating optical system into light rays of three colors, a cross dichroic prism, first, second and third liquid crystal panels arranged around the cross dichroic prism, a cooling fan, a duct for carrying a cooling fluid delivered by the cooling fan toward the first, the second and the third liquid crystal panel, and a plurality of guide members disposed in the duct to control velocities or flow rates at which the cooling fluid flows toward the first, the second and the third liquid crystal panel, respectively.
A cooling system according to the present invention is capable of optionally regulating velocities and flow rates at which air delivered by a cooling fan flows toward a plurality of liquid crystal panels so that the temperature rise of each of the plurality of liquid crystal panels is limited to the lowest possible extent.
The velocities and the flow rates are controlled so that the flow rate and the velocity at which air flows toward the G liquid crystal panel are the highest and the flow rate and the velocity at which air flows toward the R liquid crystal panel are the lowest.
These and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.